Marantz CD-73 - Strange noise while playing

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#2
Pitch and frequency goes along with the rotational speed of the CD. I think the CD clamp is dragging.
I also see that you turn a screw(?) which lifts the clamping mechanism. Why?
 
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#3
The screw is used to set the height (and weight I guess) of the clamp above the CD. I had to turn it because it wasn't properly set and so the motor had dificulties to work (you can ear it on the video when you start watching it).
 
#4
I've just tried something while the deck was playing and making the noise.
I tried to make the speed of the motor lower to ear if there was any difference. And the result is : no difference, the sound is the same. Moreovoer, the sound goes away when I go to the next track. So I guess the problem comes from the lens. But the question is : why and how fix it ?
 
#5
It sounds like the radial drive motor (the swing arm) that you can hear. Its hard to judge just how loud it is in reality but the Philips RAFOC does make those kind of noises and particularly when jumping tracks such as going to the last track on a disc. In normal play mode it should not be obvious though.

This is what you are are hearing (this is your player) and the noise is centred around 1300Hz

Are there any adjustments on these for the radial drive? (I've not got a manual in front of me)


Screenshot 2023-06-25 175143.png
 
#7
Mooly said:
This is what you are are hearing (this is your player) and the noise is centred around 1300Hz
Click to expand...

I'll be quiet after this 🙂 Its a long time since I worked on these... you start remembering things.

1300Hz, that's twice 650Hz and isn't 650Hz the frequency deliberately injected into the radial servo, with the tracking error waveform also at 650 Hz. I think that is what you are hearing
 
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#10
Hello Mooly,
Thanks for the information, the Marantz CD-73 manual is not complete and doesn't talk about lens adjustements (but it is in English at least). I can also use the Philips CD300/303 manual which is more complete but it's in German or Dutch only (I'm not lucky...). I'll have to translate it when I've got some time to kill.
Hugo, I tried what you propose but without any changes. I still can ear the noise. That let me think the noise comes from the lens.
 
#17
Its a mechanical resonance from the swing arm pivoted coil. There is a cap parallel to the output for demodulating the servo output which gets weak. The cap has been changed in value of the production run. You need to increase the value slightly as well as the filtering choke in series. Some players didn't have the coil, only the cap. Its a bipolar electrolytic. Don't remember the size.
 
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